The scores
Royal Canin Cocker Spaniel: C (58/100) — Average. Brewers rice, brown rice, and oat groats fill the top three positions. Chicken by-product meal at #4 and wheat gluten at #5 round out the formula.
Merrick: B (80/100) — Above average. Deboned chicken leads, followed by chicken meal, sweet potatoes, peas, and potatoes. Two animal proteins before any carb source.
The 22-point gap reflects a full grade-tier difference in ingredient quality. This is the gap between a grain-based formula with by-product meal and a protein-first formula with named whole meats.
How the ingredients compare
Royal Canin Cocker Spaniel: Brewers Rice, Brown Rice, Oat Groats, Chicken By-Product Meal, Wheat Gluten
Merrick: Deboned Chicken, Chicken Meal, Sweet Potatoes, Peas, Potatoes
Three grains open the Royal Canin formula before any animal protein appears at position #4 — and that protein is chicken by-product meal, not named chicken. Wheat gluten at #5 adds a plant protein booster plus a common allergen. Corn gluten meal appears further down the list, adding a second plant protein concentrate.
Merrick’s top five tells a different story: deboned chicken (whole muscle meat) and chicken meal (concentrated protein) deliver two high-quality animal protein sources first, then sweet potatoes and peas provide grain-free carbohydrates with natural fiber. No by-products, no wheat, no corn.
Where Merrick pulls ahead
Real chicken first, grain-free: Deboned chicken as #1 and chicken meal as #2 deliver protein-dense nutrition without grain fillers. For Cocker Spaniels with chronic ear infections — often linked to food allergies and inflammation — a grain-free, gluten-free formula can reduce the inflammatory triggers that contribute to ear problems.
No wheat or corn gluten: Royal Canin includes both wheat gluten and corn gluten meal, two concentrated plant proteins that are among the most common food allergens for dogs. Cocker Spaniels have one of the highest rates of food allergies among dog breeds, making these ingredients particularly problematic in a breed-specific formula.
Probiotics and natural nutrition: Merrick includes Bacillus coagulans for gut health and uses real sweet potatoes and peas for natural fiber and nutrients. Royal Canin’s formula includes no probiotics and relies on synthetic additives for its nutritional profile. Shop on Amazon →
Where Royal Canin Cocker Spaniel holds its own
The Cocker Spaniel formula includes GLA safflower oil for skin and coat health — important for a breed with a long, silky coat that requires significant care. L-carnitine supports weight management, as Cocker Spaniels are prone to obesity. Psyllium seed husk provides natural fiber, and fructooligosaccharides serve as a prebiotic.
Hydrolyzed yeast may support skin health and palatability. Glucosamine and chondroitin support joints, and the breed-specific kibble is designed for a Cocker Spaniel’s muzzle. These targeted additions address real breed concerns.
Royal Canin’s veterinary research network is also a consideration. If your Cocker has been diagnosed with a specific condition and your vet recommends this food, that clinical judgment matters. Shop on Amazon →
The bottom line
Merrick delivers significantly better ingredient quality at B/80 vs C/58. For Cocker Spaniel owners — especially those dealing with chronic ear infections, skin allergies, or food sensitivities — Merrick’s grain-free, by-product-free formula addresses the root causes of these breed-common issues better than a formula built on three grains and wheat gluten.
Royal Canin Cocker Spaniel’s GLA safflower oil and L-carnitine are valuable breed-specific additions, but both can be supplemented separately while feeding a higher-quality base diet. Read our full reviews of Royal Canin Cocker Spaniel and Merrick for the complete analysis.